universal timer

Posted on Feb 4, 2014

The time interval of this circuit can be varied digitally through the DIP switches. The time code however must be set in BCD form. A 120 Hz signal generated by doubling the line frequency is used as the time reference. This is then divided to 1 pulse per minute by the ICs 1 and 2. The counter IC3 counts backwards- that means it starts to count fro

universal timer
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m the value set by the DIP switches going back to zero. Pressing the start switch starts the counter and at the same time the triac is triggered into conduction. Once the counter reaches zero, the triac is switched off and a tone is generated. The stop button offers the possibility of forcibly stopping the counter in the middle of a counting process.

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